As the size of semiconductor devices decreases, the formation of patterns becomes more and more important. Above all, it is very important to control the critical dimensions (CD) defining gaps between lines and between spaces.
In manufacturing semiconductor devices, patterns are generally formed through a photolithography process requiring masks. That is, portions not masked with photoresist patterns are selectively etched, thereby forming patterns having desired sizes and shapes. Accordingly, the critical dimensions CD are controlled using only the photoresist patterns.
As the size of the semiconductor devices decreases, such a conventional pattern forming method more and more approaches a limit. In particular, the photolithography process has required increased exposure resolution to form finer patterns. However, it is very difficult to form such finer patterns.